The present invention generally relates to overhead doors of the type utilizing one or more counterbalancing torsion springs and, more particularly, relates to the torsion spring counterbalancing mechanism generally associated with such overhead doors as well as a winding mechanism for setting the counterbalancing force of the spring.
Overhead doors generally require a counterbalancing force which enables the door to be more easily moved between opened and closed positions either manually or by way of a powered opening device. Often, overhead door systems rely on one or more torsion springs for providing this counterbalancing force. These torsion springs must be wound during the installation of the garage door assembly such that they are provided with the necessary preset torque. Many systems require the installer to wind the spring manually by using a rod to rotate the free end of the spring with respect to a fixed end thereof and, after an appropriate number of turns, rigidly securing the free end of the spring to the torsion shaft of the overhead door assembly. This type of system is not only difficult to install but is also quite dangerous to install and remove due to the possibility of the installer inadvertently releasing the bar and being injured as a result. Thus, installers must be quite experienced to avoid the dangers involved with these prior systems.
Overhead door assemblies have been proposed in the past which have addressed problems involving manual winding of torsion springs. For example, certain gear systems have been disclosed for winding the torsion spring. Such worm gear arrangements are shown in U.S. Pat. Nos. 3,921,761; 4,882,806 and 4,981,165. In each of these systems, a ring-shaped worm gear is operatively coupled to the free end of the torsion spring and is rotated by way of a mating worm drive gear or pinion which may be driven either manually or with a power tool by the installer, Thus, rotation of the ring-shaped worm gear also rotates or winds the torsion spring to set the appropriate amount of torque in the spring.
These gear systems, however, each have disadvantages which make them impractical to use in all but the most elaborate and expensive overhead door assemblies. For example, these prior gear systems require a number of precision machined parts and further require very precise, and costly, assembly procedures. For example, the worm drive gear in each is designed to rotate about an axis perpendicular to the axis of the ring-shaped mating gear. Thus, the gear teeth on each gear must be precisely machined and matched to establish this perpendicular relationship. Additionally, the gear systems shown in U.S. Pat. Nos. 3,921,761 and 4,882,806 are designed such that the worm drive gear is oriented horizontally along an axis perpendicular to the overhead door. This makes it difficult for the installer to easily and safely apply a tool to the worm drive gear during the winding process. The worm drive gear disclosed in U.S. Pat. No. 4,981,165 is also shown in a horizontal orientation but also actually rotates with the torsion shaft and therefore this system includes the further undesirable possibility of leaving the worm drive gear in an even more inaccessible orientation. Also, each of the worm gear systems described in the above patents leaves open the possibility of undesirable rotation of the worm drive gear and ring-shaped gear and a resulting unwinding action of the torsion spring after the system has been wound. This may occur, for example, by the vibration caused during everyday operation of the overhead door. Finally, none of these prior systems provide an easy manner of identifying the number of turns that have been made in the torsion spring. Further disadvantages of these systems will become more apparent upon review of the advantageous features of the present invention.
Overhead door assemblies prior to the present invention have also utilized torsion springs in which adjacent coils thereof abut one another when the spring is in a normal, unwound resting state. In other words, these springs have been manufactured in the past such that there is no gap left between adjacent coils. Therefore, during the initial winding process and during operation of the overhead door, frictional force arising as the result of rubbing action between adjacent coils of the shrinking spring must be overcome by the system. This places the system under additional stresses and strains which must be borne by the spring itself as well as the user or the powered door opener, each of which is undesirable. The additional stress that the abutting coils place on the spring may lead to a shorter effective spring life and/or premature failure of the spring.
Many prior systems not only use springs having abutting coils but further fail to provide for the growth and contraction of the torsion spring during the operations of initially winding the spring and of spring unwinding and winding during raising and lowering of the door. Other systems that do provide some means for accommodating spring growth and contraction tend to be suitable for one operation but not the other or tend to be complicated systems which are impractical in many applications, such as residential applications, and which create new problems associated with their complicated design and installation procedures.
A need in the art therefore exists for improvements which, for example, allow easier installation of overhead door systems as well as improved operation thereof while maintaining low overall costs and a long useful life.